Human Reproductive System

Every organ system in the human body works continuously to maintain internal balance for the survival of the individual, but the reproductive system exists for a different reason: it is essential for the survival of the species, not the individual — a person can live a full, healthy life without ever reproducing, yet reproduction remains essential for a species to continue existing at all. The reproductive system carries out four main functions: producing the gametes (sperm and ova), transporting and sustaining those gametes, nurturing the developing offspring, and producing hormones. Its work unfolds as a sequence of named events — gametogenesis, insemination, fertilisation, cleavage, implantation, placentation, gastrulation, organogenesis and finally parturition. Two kinds of organs carry this out: the primary reproductive organs (the testis in the male, the ovary in the female), which actually produce the gametes, and a supporting cast of accessory organs and glands that transport and sustain the gametes and nurture the offspring. Hormones from the pituitary gland and the gonads control the development of secondary sexual characteristics and the day-to-day running of the whole reproductive system.